<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>bootstrap4网格系统练习1</title>
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <link rel="stylesheet" href="https://cdn.bootcss.com/twitter-bootstrap/4.3.1/css/bootstrap.min.css">
    <link rel="stylesheet" href="css/style.css">
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
            <div class="col-6 col-sm-4 col-md-3">内容</div>
        </div>
    </div>
</body>
</html>